Of course not Ms Sphinx - only more human.
Thinking about it further, it was a funny match - a day of statistical anomalies. I play on grass, so we get bad bounces, but in one game I lost three straight points and the game, all on bad bounces on my side. (I then uttered a profanity).
In another game I held to love serving four unreturnables -three in a row of which hit the lines.
Just one of those days.

Damnit! I've been playing/practicing rec-club tennis from 8:30 to 12:30 today and on my last serve of the day, was shooting for four double-faults in one game. I lost track of the score and only got three in before it was set point--that's what happens when you're tired, lose track of the score and don't keep your head up long enough. At least they were all into the tape and nearly identical--humble brag.

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"...the human emotional system was not designed to endure the mental rigors of a tennis match." Dr. Allen Fox

were your legs cramping? not getting the same lift on your serve? shoulder tired? battling fatigue? someone at your advanced age (with all those easy 2 set wins) maybe struggled with just being tired in a close match???

I double fault more due to nerves during matches, than when playing for fun (be it right afterwards- at that point I'm more relaxed and my serve technique and rhythm are better, including more bending of the knees etc)

...we should not use the words "never" or "always." Stuff happens, and afterwards, you can make up any kind of story you want, still, what happened did happen. It's over and there's no looking back. We can all improve our serves...and our backhands, forehands, and so forth. But if you miss a shot at a crucial time in the match, that's the way it goes. Let it go, and drive on...

Double faults are my staple while I'm still working on my serve. My goal is not just to hit the ball in but to serve a weapon. Just last Saturday, playing 3 doubles sets , I served about 2 or 3 doubles per game on average, and lost many of my service games, in windy conditions. Still working on adapting my serve to the wind.

I don't feel under pressure to hold my serves because I'm very confident in the rest of my game, so I feel free to experiment. Ended up winning my sets quite comfortably, despite losing a few service games.

Also, in doubles, serving is tricky because you rely so much on your partner at the net. If you don't trust your partner, then you feel more inclined to go for too much. While you're still improving and experimenting with your serve, don't worry about double faults and losing your games. Pay attention to what you're doing wrong on the second serve and try to adjust/work on it. I usually hit the second serve into the net, cos I put too much spin on it and not enough power.